ALTAIR Center in cooperation with the University of Rochester proposes to develop the first silicon-based photonic crystal laser diode. The photonic crystal microcavity forms gain region of the laser diode. This enhances the system efficiency. The laser operating either in bandgap edge emitting mode with enhanced density of states or using defect mode in the photonic crystal structure will exhibit dramatically reduced threshold and improved beam quality. In our previous research projects we already fabricated a model Er-doped silicon-based one-dimensional photonic crystal with the defect mode. We also experimentally demonstrated luminescence enhancement and narrowing of the emission linewidth. Capitalizing on the developed technologies and combining expertise of our teams will ensure successful development of a prototype silicon-based photonic crystal laser for both military and commercial applications. In Phase I of this Project, we will perform numerical simulations, analysis, and design of the proposed silicon-based photonic crystal laser diode, fabricate the photonic crystal microstructures and characterize their luminescence under optical pump. In Phase II, the developed technology will be completely optimized and applied to fabrication of an electrically pumped prototype silicon-based photonic crystal laser diode